Microembolic signals and strategy to prevent gas embolism during extracorporeal membrane oxygenation

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) supplies systemic blood perfusion and gas exchange in patients with cardiopulmonary failure. The current literature lacks of papers reporting the possible risks of microembolism among the complications of this treatment. In this study we present our preliminary experience on brain blood flow velocity and emboli detection through the transcranial Doppler monitoring during ECMO. METHODS: Six patients suffering of heart failure, four after cardiac surgery and two after cardiopulmonary resuscitation were treated with ECMO and submitted to transcranial doppler monitoring to accomplish the neurophysiological evaluation for coma. Four patients had a full extracorporeal flow supply while in the remaining two patients the support was maintained 50% in respect to normal demand. All patients had a bilateral transcranial brain blood flow monitoring for 15 minutes during the first clinical evaluation. RESULTS: Microembolic signals were detected only in patients with the full extracorporeal blood flow supply due to air embolism. CONCLUSIONS: We established that the microembolic load depends on gas embolism from the central venous lines and on the level of blood flow assistance. The gas microemboli that enter in the blood circulation and in the extracorporeal circuits are not removed by the membrane oxygenator filter. Maximum care is required in drugs and fluid infusion of this kind of patients as a possible source of microemboli. This harmful phenomenon may be overcome adding an air filter device to the intravenous catheters.